Back-spacing mechanism.



C. SPIRO. BACK SPAUING MEGHANISNL. urpzoumn FILED JULY 26, 1910.

' Patented Mar. 28, 1911.

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To all whom ttlmc'y concern:

Be it known that 1, CHARLES Srmo, a'citizen of the United States, residing at New York, county of New York, State of New York, have invented certain new and useful Improvements in Back-Spacing Mechanism, of which the following is a specification, reference being had therein to the accompanying drawing.

This invention relates broadly to theart.

oftyp'ewriting machines and specifically to back spacing mechanisms wherein the carriage of the typewriter is adapted to be "moved step-by-step in a direction opposite to the movement of the carriage when under the influence of the letter spacing mechanisms.

The principal object of the invention is to provide an efficient back spacing mechanism construct a back spacing mechanism in which the rack engaging dog is formed In- 35' tegral with the carrying link therefor.

A further object of this invention is to construct 'a back spacing mechanism in' which the back spacing (10g maybe resiliently held in engagement with the back spacing rack.

A further object of this invention is to construct a back spacing mechanism in such manner that the back spacingdog will immecliately leave the back spacing rack as soon as the pressure is relieved upon the back space key.

A still further object of this invention isto construct a back spacingmechanism in such manner that the back spacing dog may automatically ad3ust its engaging teeth to the position of the back spacing rack in order that the engaging parts may not be injured by being forced into abnormal positive engagement with each other.

Other objects of the invention will in part be obvious and-will in part be pointed out in reference tojthe accompanying 'drawlngs which forma part thereof, and the scope of the invention will lie-indicated by the appended claim-s.

Throughout the several figures of the drawings like numerals are used to indicate like parts.

Figure 1 is a plan view of theback spacing mechanism. Fig. 2 is a view showing the mechanism in Fig. l in elevation. Fig. 3 is a view showing the back spacing dog in elevation in its relation to the'back spacing rack. Fig. 4 is a detail plan view of the back spacingdog. Fig. 5 is a detail view showing the back spacing dog irrelcvation. 6 is aplan view of the adjustable stop. Fig. 7 is a view showing the adjustable stop in elevation.

As this invention is restricted specifically to back spacing mechanism for typewriting machines, the back spacing mechanism only. has been illustrated. The other portions of the typewriting machine which are well known in the art are omitted from the drawings, with the exception of certain portions of the machine frame, which. have been indicated byiiotted lines.

J Referring specifically to Figs. 1 and 2 of the drawings, a back spacing lever 1 is provided on its forward end with a finger or frame 3, by means of a pivot member i. The rear end of the back spacing lever l, is

I adapted to be connected with a longitudiformed with a. raised curved. portion 10, which is provided with a toothed head 11, the teeth of which are adapted to conform and mesh with teeth formed upon a back spacing rack 12. The back spacing rack '12, may be an independent rack. adapted for the purpose of backspacing only, or it may be the rack which is engaged by the escapement dogs for controlling the toe the specification hereinafter following, by

thumbpiece 2, and is pivtited to the machine The outer end of the link dog carrieris ward letter spacing. However, the structure specifically illustrated in the drawings refers to a rack which is independent of the usual rack en aged by the-escapement dogs which sontro ls the carriage in its letter spacing movement,

The slot 9 is formed at its outer end into a downwardly curved portion 14, which meet-sthe parallel upper and lower sides and 16 of the slot. A carriage top plate 3 .-of the machine, is provided with a downwardly depending bracket 17, which -terms a carrying support for a stud screw 1.8, that is adapted to pass through the controlling slot 9 in the dog carrying link 5. -A re- -tract1ng coiled spring 19, is attached to position upon the side of the link dog carrier 5.- The outer end of the adjustable stop member 22," is curved as at 28, in such manner that the upper portion of the curve overhangs to a slight degree the lower por tion of the curve. The curve face 28 is adapted to engage with the stud screw 13 when the dog carrier has reached its limit of travel, and the overhanging upper portion of the curve 28 is constructed to so fit over the stud screw 18 as to substantially lock the toothed head 11 in firm engage- .ment with the teeth of the back spacing rack 12, in order'td prevent any overthrow of the carriage when the" back spacing mechanism is violently actuated.

Theuoperation of the device is' substantially as follows :-As the thumb piece 2,

of the back spacing lever 1, is pushed in an outward d1rection,'- the back spacing lever is swung upon its pivot 4:, and the moving dog carrier 5, is given a longitudinal movement in a direction opposite to the normal movement of the typewriter carriage when moving under the influence 01'' the usual carriage spring drum (not illustrated). The link 'dog carrier at this time is under the influence of two forces, a. 0., the'torce on the finger key tending to move the dog carrier forward, and the force of the retracted spring 19 tending to pull the dog carrier upward. The result of these forces is to-cause the stud screw 18 to ride downward over the curved wall 1 of the slot 9, in such manner that the toothed head 11 comes into engagement with the teeth on the backspacing rack 12. It will be noted that one of the forces tending to member in a predetermined fixed back spacing rack, resilientmeans for causbring'thcso engaging teeth together, is that of the coiled spring 15 and therefore if the teeth on the rack 12 are not in a proper position to engage the toothed head 11, the

engaging teeth on the head immediately yield suliic-iently to prevent the binding action which frequently occurs wherein back spacing mechanisms are arranged to drive the back spacing dog into positive engagement with the backspacing rack. VAfter the head 11 has engaged the back spacing.

rack, the carriage to which this rack is attached, is forced to move under the influence of linger pressure until the curved face id, on the adjustable stop member 22, comes into engagement with the stud screw 18, at which time the teeth on the head 11 are positively cammed or locked in engagement-- with the teeth on the rack 12, because of the wedging action due to the overhan $5 ing portion of the curved face in its engagement with the head oi the stud screw 18. Immediately as pressure is released from the finger key, one of the component forces which has been holding the head 11 in engagement with the rack 12, disappears, and the engaging head immediately drops away from the rack and the several parts are returned to their normal position, due to the influence of the retracted spring 19.

Having thus describedmy invention what I desire'ctoclaim as new and secure by Letters Patent is 1- 1. In a back spacingfinechanism for a typewriting machine, the combination of an operatingilever, a dog carrying link, means operatively connecting said operating lever with said dog carrying link, a back spacing dog carried by'said dog carrying 'llllk, a 5

ing said back spacing dog to engage said back spacing'rack, an adjustable stop member carried by'said' dog carrying link, and means cooperating with said adjustable stop member to lock said dog inengagement it said rack.

2. In a back spacing mechanism for a typewriting machine, the combination of an operating lever, a link, means operatively connecting said lever with said link, aback spacing dog carried by said link, a back spacing rack, resilient means for causing said backspacing dog to engage said back spacing rack, and adjustable means for limiting the extent of movement of said back spacing dogand locking said dog in engagement with said rack only at the end of its spacing movement.

3. In a back spacing mechanism for a" F typewriting machineFthe combination of an operating lever with aI link, a dog carried by 4 said link, a back spacing rack, resilient means for causing said dog to engage with said back spacing rack, andadjustable means carried by said dog for locking it in 'engagement with said rack at the end of theitravel ofsaid dog toward the rack.

4. In a back spacing mechanism for a typewriting machine, the combination of an operating lever, with a dog carrying link, pivotal means connecting said lever to said link, a back spacing dog formed integral with said back spacing link, said back spac' ing link being formed with a slot having one wall curved, a guiding stud adapted to cooperate with the walls of said slot, a spring member for holding the walls of said slot in engagement with said stud, a back spacing rack, the arrangement and construction of parts being such that the back spacing dog is resiliently thrown into contact with said back spacing rack when the operating lever is act-uatedf In a back spacing. mechanism for a typewriting machine, the combination of an operating lever, a dog carrying link, pivotal means for attaching s'aid operating lever to .said dog carrying link, a back spacing dog carried by said dog carrying link, said dog carrying link being provided with a slot, one wall of which is curved,'a guiding stud of less diameter than the Width of said slot, and adapted to engage one wall of said slot, a back spacing rack, a resilient member having one end connected to said dog carryin'g link in such manner as to cause said back spacing dog to engage said back spacing rack when said operating lever is actuated, and an adjustable stop member adapted to limit the degree of movement of said backspacing dog carrier.

6. In a back spacing mechanism for a typewriting machine, the combination of an operating lever, a dog carrying link, pivotal means for attaching said operating lever to said dog carrying link, a back spacing dog formed integral with said link, a rack, a.

portion of said dog carrying link being formed with a curved wall, means cooperating with said curved wall to guide the direction of movement of said link, and resilient means for maintaining said curved,

wall in contact with said guiding means during the actuation 'of said back spacing mechanism.'

7. Ina back spacing mechanism for a typewriting machine, thecombination of an operating lever, with a dog carryin guiding means adapted to contact with said curved wall, means for maintaining said curved wall in contact with said guiding means, and a wedged-shaped cammember constructed in such manner as to cause said back spacing dog to be substantially locked in engagement with said back spaclng rack when said'dog carrying link has reached its limit of travel in its back spacing movement.

In testimony whereof I aifix my signature in presence of two witnesses.

'GHARLES SPIRO. Witnesses: I

EDWIN E. JoN'Es, FRANK H. Connm. 

